Conventionally, there has been known a MOSFET which includes a semiconductor base substrate where a super junction structure is formed of an n-type column region and a p-type column region (see patent document 1, for example).
As shown in FIG. 10, a conventional MOSFET 800 includes: a semiconductor base substrate 810 having n-type column regions 814, p-type column regions 816, a p-type base region 818 formed on surfaces of the n-type column regions 814 and surfaces of the p-type column regions 816, and an n-type source region 820 formed on a surface of the base region 818 and where a super junction structure is formed of the n-type column regions 814 and the p-type column regions 816; trenches 822 which are formed so as to reach a depth position deeper than a deepest portion of the base region 818 in regions where the n-type column region 814 is positioned as viewed in a plan view and a part of the source region 820 is exposed on an inner peripheral surface of the trench 822; and gate electrodes 826 which are embedded in the inside of the trenches 822 by way of the gate insulation films 824 formed on inner peripheral surfaces of the trenches 822.
In the conventional MOSFET 800, the n-type column region 814 and the p-type column region 816 are formed such that a total amount of a dopant in the n-type column region 814 is equal to a total amount of a dopant in the p-type column region 816. That is, the n-type column region 814 and the p-type column region 816 are well-balanced with each other in terms of a charge.
In this specification, “super junction structure” means a structure where an n-type column region and a p-type column region are alternately and repeatedly arranged as viewed in a predetermined cross section. Further, “total amount of a dopant” means a total amount of a dopant contained in a constitutional element (the n-type column region or the p-type column region) in the MOSFET.
According to the conventional MOSFET 800, the MOSFET includes the semiconductor base substrate 810 where the super junction structure is formed of the n-type column region 814 and the p-type column region 816 and hence, it is possible to provide a switching element having a low ON resistance and a high withstand voltage.